This tutorial uses a Logitech USB headset that combines a microphone with headphones and plugs into the computer using a USB connection. Macintosh computers do not have a direct microphone input jack. Even though your computer may include a built-in microphone, using a dedicated microphone isolates your voice and reduce background noise and is really a requirement for a good podcast.
To begin using the headset with the Mac, first plug the headset into an available USB port on your computer. Do not use the slower USB connection on the keyboard.
Next, configure the sound preferences to enable the headset. Click the blue Apple icon at the top left corner of the screen. Then select System Preferences.
In the Hardware section, click Sound.
in the Sound Preference Pane (below) click Output. Choose the option that matches where you want to the sound playback, in this example the headphones on the Logitech USB Headset. Any sound will be heard through the headphones.
Next click Input and again choose Logitech USB Headset.
Now you can to speak into your microphone and see the sound Input Level in the Sound Preferences pane. You may need to return to this panel to configuring recording audio levels in GarageBand.
When you are finished monitoring your podcast recording through your headset, you will need to reset the output back to the internal speakers.
With the microphone input and headset monitoring properly set up, you can record and monitor podcast narration in a GarageBand track.